This disclosure relates generally to vapor compression systems and, more particularly, to flooded start management of a compressor in a refrigerant vapor compression system.
Conventional vapor compression systems typically include a compressor, a heat rejection heat exchanger, a heat absorption heat exchanger, and expansion device disposed upstream with respect to working fluid flow of the heat absorption heat exchanger and downstream of the heat rejection heat exchanger. These basic system components are interconnected by working fluid lines in a closed circuit, arranged in accord with known vapor compression cycles. Vapor compression systems charged with a refrigerant as the working fluid are commonly known as refrigerant vapor compression systems.
Refrigerant vapor compression systems are commonly used for conditioning air to be supplied to a climate controlled comfort zone within a residence, office building, hospital, school, restaurant or other facility. Refrigerant vapor compression system are also commonly used for refrigerating air supplied to display cases, merchandisers, freezer cabinets, cold rooms or other perishable/frozen product storage areas in commercial establishments. Refrigerant vapor compression systems are also commonly used in transport refrigeration systems for refrigerating air supplied to a temperature controlled cargo space of a truck, trailer, container or the like for transporting perishable/frozen items by truck, rail, ship or intermodal. Refrigerant vapor compression systems used in connection with transport refrigeration systems are generally subject to more stringent operating conditions than in air conditioning or commercial refrigeration applications due to the wide range of operating load conditions and the wide range of outdoor ambient conditions over which the refrigerant vapor compression system must operate to maintain product within the cargo space at a desired temperature.
In all vapor compression systems, the compressor is designed for compressing working fluid received at the suction inlet of the compressor in vapor state at a relatively lower pressure. The working fluid vapor is compressed and discharged from the compressor as a relatively higher pressure vapor. However, if the vapor compression system is started after an extended period time in during which the compressor has not been operating, working fluid trapped in the compressor when the system was shut down, as well as working fluid that may have migrated into the compressor during the extended period of shutdown, will accumulate in the compressor sump in a liquid state. Typically, a flooded refrigerant compressor may have from as little as one pound of refrigerant up to ten pounds of refrigerant accumulated in the compressor sump. Consequently, upon start-up of the compressor after the vapor compression system has been shut down for an extended period of time, liquid working accumulate within the sump can be drawn into the compression mechanism of the compressor. A start of the compressor with liquid working accumulated in the compressor sump is commonly referred to a “flooded start”. A flooded start of the compressor is undesirable for several reasons, including the potential for permanent damage to the compression elements. Also, flooded starts are noisy.